The present invention relates to a conductive sheet, a touch panel and a display device.
In recent years, electronic apparatuses including a touch panel have become widely used. The touch panel is mounted in many apparatuses including a small-size screen, such as a mobile phone or a personal digital assistant (PDA). In the future, the mounting of the touch panel in apparatuses including a large-size screen, such as a display for a personal computer (PC), is sufficiently expected.
As a conventional touch panel electrode, in terms of optical transparency, an indium tin oxide (ITO) is mainly used. It is known that the electric resistance per unit area of the ITO is relatively high compared with those of metals and the like. That is, in the case of the ITO, as the size of the screen (total area of the touch panel) increases, the surface resistance of the entire electrode increases. As a result, since the transmission rate of the current between electrodes is reduced, a problem that the time until the contact position is detected after touching the touch panel (that is, response speed) increases becomes noticeable.
Therefore, various techniques for reducing the surface resistance by configuring electrodes by forming a number of mesh lattices with a thin wire (thin metal wire) that is formed of a metal with low electric resistance have been proposed. For example, when an object for observation is a display screen, mesh shapes are made to have irregularities in order to suppress the generation of moire (interference fringes) due to the geometrical relationship with each pixel that constitutes the display screen.
As shown in FIG. 43A, US 2011/0102361 A discloses a mesh pattern 4 formed by combining a plurality of thin wires 1, which are disposed so as to extend horizontally at random, and a plurality of thin wires 2, which are disposed so as to extend vertically at random.
As shown in FIG. 43B, US 2009/0219257 A discloses a mesh pattern 8 which is filled with polygonal mesh shapes without any space in a belt-like region 6 where the contact of a conductor (not shown) and the like can be detected.
However, when the sizes of openings determined by the mesh shapes are approximately same like in the mesh pattern 4 disclosed in US 2011/0102361 A, color noise has been generated in some cases due to the relationship with the regularity of the arrangement of respective subpixels (for example, RGB subpixels) of a pixel.
When the sizes of the openings are excessively vary like in the case of the mesh pattern 8 disclosed in US 2009/0219257 A, there is a disadvantage in that granular feeling of noise (also referred to as feeling of roughness) is easily recognized.